Method and apparatus for an improved upper electrode plate with deposition shield in a plasma processing system

[0001] This application is related to co-pending U.S. patent application Ser. No. 10/259,757, entitled “Method and apparatus for an improved upper electrode plate in a plasma processing system”, filed on even date herewith; co-pending U.S. patent application Ser. No. 10/259,392, entitled “Method and apparatus for an improved baffle plate in a plasma processing system”, filed on even date herewith; co-pending U.S. patent application Ser. No. 10/259,380, entitled “Method and apparatus for an improved baffle plate in a plasma processing system”, filed on even date herewith; co-pending U.S. patent application Ser. No. 10/259,353, entitled “Method and apparatus for an improved deposition shield in a plasma processing system”, filed on even date herewith; co-pending U.S. patent application Ser. No. 10/259,352, entitled “Method and apparatus for an improved optical window deposition shield in a plasma processing system”, filed on even date herewith; and co-pending U.S. patent application Ser. No. 10/259,306, entitled “Method and apparatus for an improved bellows shield in a plasma processing system”, filed on even date herewith. The entire contents of all of those applications are herein incorporated by reference in their entirety.

[0002] The present invention relates to an improved component for a plasma processing system and more particularly to an upper electrode with a deposition shield employed in a plasma processing system to introduce a processing gas and protect a chamber interior.

[0003] The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a plasma reactor necessary to remove material from and deposit material to a substrate. In general, plasma is formed within the plasma reactor under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions and, therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the chamber (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).

[0004] Although the formation of a population of charged species (ions, etc.) and chemically reactive species is necessary for performing the function of the plasma processing system (i.e. material etch, material deposition, etc.) at the substrate surface, other component surfaces on the interior of the processing chamber are exposed to the physically and chemically active plasma and, in time, can erode. The erosion of exposed components in the plasma processing system can lead to a gradual degradation of the plasma processing performance and ultimately to complete failure of the system.

[0005] In order to minimize the damage sustained by exposure to the processing plasma, components of the plasma processing system, known to sustain exposure to the processing plasma, are coated with a protective barrier. For example, components fabricated from aluminum can be anodized to produce a surface layer of aluminum oxide, which is more resistant to the plasma. In another example, a consumable or replaceable component, such as one fabricated from silicon, quartz, alumina, carbon, or silicon carbide, can be inserted within the processing chamber to protect the surfaces of more valuable components that would impose greater costs during frequent replacement. Furthermore, it is desirable to select surface materials that minimize the introduction of unwanted contaminants, impurities, etc. to the processing plasma and possibly to the devices formed on the substrate.

[0006] In both cases, the inevitable failure of the protective coating, either due to the integrity of the protective barrier or the integrity of the fabrication of the protective barrier, and the consumable nature of the replaceable components demands frequent maintenance of the plasma processing system. This frequent maintenance can produce costs associated with plasma processing down-time and new plasma processing chamber components, which can be excessive.

[0007] The present invention provides an improved upper electrode with a deposition shield for a plasma processing system, wherein the design and fabrication of the upper electrode advantageously addresses the above-identified shortcomings.

[0008] It is an object of the present invention to provide the improved upper electrode comprising an electrode plate and a deposition shield. The electrode plate comprises a first surface for coupling the electrode plate to an upper assembly, a second surface, opposite the first surface, comprising a plasma surface configured to face a processing plasma in the plasma processing system and a mating surface for mating with the plasma processing system, and a peripheral edge. The deposition shield comprises a cylindrical wall coupled to the electrode plate and configured to extend therefrom. The cylindrical wall comprises an inner surface contiguous with the plasma surface of the electrode plate, an outer surface contiguous with the mating surface of the electrode plate, and a distal end surface, wherein the distal end surface can comprise a distal end lip surface.

[0009] The electrode plate can further include a plurality of gas injection orifices, wherein at least one gas injection orifice comprises an entrant region for receiving a processing gas and an exit region for coupling the processing gas to the plasma processing system, the exit region comprising an injection surface.

[0010] The electrode plate can further include a plurality of fastening receptors for receiving fastening devices in order to attach the electrode plate with the deposition shield to the upper electrode.

[0011] The electrode plate can further include one or more fastening through-holes for receiving fastening devices in order to attach the electrode plate with the deposition shield to the plasma processing system.

[0012] The electrode plate can further include a plenum cavity coupled to the first surface, configured to receive the processing gas, and configured to distribute the processing gas to the plurality of gas injection orifices.

[0013] The electrode plate can further include a first sealing feature coupled to the first surface of the electrode plate and configured to seal the electrode plate with the upper assembly, a second sealing feature coupled to the first surface of the electrode plate and configured to seal the electrode plate with the upper assembly, and one or more third sealing features coupled to the first surface of the electrode plate and configured to seal the one or more fastening through-holes with the upper assembly.

[0014] The electrode plate can further comprise a diagnostics port, and a fourth sealing feature coupled to the first surface of the electrode plate and configured to seal the diagnostics port with the upper electrode. The diagnostics port can include an entrant cavity and an exit through-hole comprising an interior surface.

[0015] It is another object of the present invention to further provide an electrode plate with a deposition shield comprising an opening in the deposition shield for enabling access to the process space through the deposition shield. The opening can comprise a first opening surface, a second opening surface, and a mating surface, wherein the mating surface can comprise one or more tapped holes comprising a fastening surface.

[0016] The electrode plate can further comprise a protective barrier formed on a plurality of exposed surfaces of the electrode plate with the deposition shield facing the processing plasma.

[0017] It is a further object of the present invention that the exposed surfaces of the electrode plate with the deposition shield comprise the plasma surface of the second surface of the electrode plate, the inner surface of the cylindrical wall of the deposition shield, and the distal end lip surface of the distal end surface of the deposition shield. Additionally, the exposed surfaces can comprise the injection surface of the exit region in the plurality of gas injection orifices, the interior surface of the exit through-hole in the diagnostics port, the first opening surface of the opening, and the mating surface excluding the fastening surface of the opening in the deposition shield.

[0018] The present invention provides a method of producing the electrode plate with the deposition shield for the upper electrode in the plasma processing system comprising the steps: fabricating the electrode plate with the deposition shield; anodizing the electrode plate with the deposition shield to form a surface anodization layer on the electrode plate with the deposition shield; machining exposed surfaces on the electrode plate with the deposition shield to remove the surface anodization layer; and forming a protective barrier on the exposed surfaces. The present invention may also optionally include machining the first surface of the electrode plate excluding the plenum cavity, the first sealing feature, the second sealing feature, the one or more third sealing features, the fourth sealing feature, and the distal end mating surface.

[0019] The present invention provides another method of producing the electrode plate with the deposition shield for the upper electrode in the plasma processing system comprising the steps: fabricating the electrode plate with the deposition shield; masking the exposed surfaces on the electrode plate with the deposition shield to prevent formation of a surface anodization layer; anodizing the electrode plate with the deposition shield to form the surface anodization layer on the electrode plate with the deposition shield; unmasking the exposed surfaces; and forming a protective barrier on the exposed surfaces. The present invention may also optionally include masking other non-exposed surfaces (e.g., the first surface of the electrode plate excluding the plenum cavity, the first sealing feature, the second sealing feature, the one or more third sealing features, the fourth sealing feature, and the distal end mating surface).

[0020] The present invention provides another method of producing the electrode plate with the deposition shield for the upper electrode in the plasma processing system comprising the steps: fabricating the electrode plate with the deposition shield; and forming a protective barrier on the exposed surfaces.

[0021] The present invention may also include a process of combining machining and masking to prepare the exposed surfaces to receive the protective barrier, and then forming the protective barrier on the exposed surfaces. For example, two of the exposed surfaces can be masked prior to anodizing, and two of the surfaces can be machined after anodizing to create four exposed surfaces on which the protective barrier can be formed.

[0035] The present invention provides an improved upper electrode for a plasma processing system, wherein the design and fabrication of the upper electrode advantageously addresses known shortcomings.

[0036] According to an embodiment of the present invention, a plasma processing system 1 is depicted in FIG. 1 comprising a plasma processing chamber 10, an upper assembly 20, an upper electrode 22, a substrate holder 30 for supporting a substrate 35, and a pumping duct 40 coupled to a vacuum pump (not shown) for providing a reduced pressure atmosphere 11 in plasma processing chamber 10. Plasma processing chamber 10 can facilitate the formation of a processing plasma in a process space 12 adjacent substrate 35. The plasma processing system 1 can be configured to process various substrates (i.e., 200 mm substrates, 300 mm substrates, or larger).

[0037] In the illustrated embodiment, upper electrode 22 comprises an electrode plate 24 (FIG. 2) with a deposition shield 26 (FIG. 2). In an alternate embodiment, upper assembly 20 can comprise at least one of a cover, a gas injection assembly, and an upper electrode impedance match network. For example, the upper electrode 22 can be coupled to an RF source. In another alternate embodiment, the upper assembly 20 comprises a cover and an upper electrode 22, wherein the upper electrode is maintained at an electrical potential equivalent to that of the plasma processing chamber 10. For example, the plasma processing chamber 10, the upper assembly 20, and the upper electrode 22 can be electrically connected to ground potential.

[0038] Plasma processing chamber 10 can, for example, further comprise an optical viewport 16. Optical viewport 16 can comprise an optical window 17 coupled to the backside of an optical window deposition shield 18, that can be coupled to deposition shield 26, and an optical window flange 19 can be configured to couple optical window 17 to the optical window deposition shield 18. Sealing members, such as O-rings, can be provided between the optical window flange 19 and the optical window 17, between the optical window 17 and the optical window deposition shield 18, and between the optical window deposition shield 18 and the plasma processing chamber 10. Optical viewport 16 can, for example, permit monitoring of optical emission from the processing plasma in process space 12.

[0039] Substrate holder 30 can, for example, further comprise a vertical translational device 50 surrounded by a bellows 52 coupled to the substrate holder 30 and the plasma processing chamber 10, and configured to seal the vertical translational device 50 from the reduced pressure atmosphere 11 in plasma processing chamber 10. Additionally, a bellows shield 54 can, for example, be coupled to the substrate holder 30 and configured to protect the bellows 52 from the processing plasma. Substrate holder 10 can, for example, further be coupled to at least one of a focus ring 60, and a shield ring 62. Furthermore, a baffle plate 64 can extend about a periphery of the substrate holder 30.

[0040] Substrate 35 can be, for example, transferred into and out of plasma processing chamber 10 through a slot valve (not shown) and chamber feed-through (not shown) via robotic substrate transfer system where it is received by substrate lift pins (not shown) housed within substrate holder 30 and mechanically translated by devices housed therein. Once substrate 35 is received from substrate transfer system, it is lowered to an upper surface of substrate holder 30.

[0041] Substrate 35 can be, for example, affixed to the substrate holder 30 via an electrostatic clamping system. Furthermore, substrate holder 30 can, for example, further include a cooling system including a re-circulating coolant flow that receives heat from substrate holder 30 and transfers heat to a heat exchanger system (not shown), or when heating, transfers heat from the heat exchanger system. Moreover, gas can, for example, be delivered to the back-side of substrate 35 via a backside gas system to improve the gas-gap thermal conductance between substrate 35 and substrate holder 30. Such a system can be utilized when temperature control of the substrate is required at elevated or reduced temperatures. In other embodiments, heating elements, such as resistive heating elements, or thermoelectric heaters/coolers can be included.

[0042] In the illustrated embodiment, shown in FIG. 1, substrate holder 30 can comprise an electrode through which RF power is coupled to the processing plasma in process space 12. For example, substrate holder 30 can be electrically biased at a RF voltage via the transmission of RF power from a RF generator (not shown) through an impedance match network (not shown) to substrate holder 30. The RF bias can serve to heat electrons to form and maintain plasma. In this configuration, the system can operate as a reactive ion etch (RIE) reactor, wherein the chamber and upper gas injection electrode serve as ground surfaces. A typical frequency for the RF bias can range from 1 MHz to 100 MHz and is preferably 13.56 MHz. RF systems for plasma processing are well known to those skilled in the art.

[0043] Alternately, the processing plasma formed in process space 12 can be formed using a parallel-plate, capacitively coupled plasma (CCP) source, an inductively coupled plasma (ICP) source, any combination thereof, and with and without DC magnet systems. Alternately, the processing plasma in process space 12 can be formed using electron cyclotron resonance (ECR). In yet another embodiment, the processing plasma in process space 12 is formed from the launching of a Helicon wave. In yet another embodiment, the processing plasma in process space 12 is formed from a propagating surface wave.

[0044] Referring now to an illustrated embodiment of the present invention depicted in FIGS. 2 (plan view) and 3 (cross-sectional view), upper electrode 22 comprises a cylindrical element having an electrode plate 24 and a deposition shield 26. The electrode plate 24 can comprise a first surface 82 for coupling the upper electrode 22 to the upper assembly 20, a second surface 88 comprising a plasma surface 90 configured to face the processing plasma in the plasma processing chamber 10 and a mating surface 92 for mating the upper electrode 22 with the plasma processing chamber 10, and a peripheral edge 94. The deposition shield 26 can comprise a cylindrical wall 70 coupled to electrode plate 24 and configured to extend therefrom. The cylindrical wall 70 can comprise an inner surface 72 contiguous with the plasma surface 90 of the electrode plate 24, an outer surface 74 contiguous with the mating surface 92 of the electrode plate 24, and a distal end surface 76.

[0045] FIG. 4 provides an expanded view of the deposition shield 26 coupled to the electrode plate 24. As shown in FIG. 4, distal end surface 76 of cylindrical wall 70 further comprises a distal end mating surface 77 and a distal end lip surface 78, wherein the distal end lip surface 78 is contiguous with the inner surface 72 of the cylindrical wall 70. Alternately, electrode plate 24 with deposition shield 26 can further comprise one or more fastening through-holes 112 configured to extend the length of the cylindrical wall 70 and configured to receive fastening devices (not shown), such as a bolt, etc., in order to couple the upper electrode 22 to the plasma processing system 1. Each fastening through-hole 112 can comprise a first entrant fastening cavity 113, a second entrant fastening cavity 114, a third entrant fastening cavity 115, and a fastening passage 116. For example, the number of fastening through-holes 112 formed within electrode plate 24 can range from 1 to 100. Desirably, the number of fastening through-holes 112 can range from 5 to 20; and, preferably the number of fastening through-holes 112 is at least 8.

[0046] With continuing reference to FIGS. 2 and 3, and as shown in FIG. 5, the electrode plate 24 further includes a plurality of gas injection orifices 100 coupled to the first surface 82 and the second surface 88, wherein each gas injection orifice 100 comprises an entrant region 102 for receiving a processing gas and an exit region 104 for coupling the processing gas to the plasma processing chamber 10. Furthermore, the interior surface of each gas injection orifice 100 can comprise an injection surface 106, a first entrant surface 107, and a second entrant surface 108. The processing gas can, for example, comprise a mixture of gases such as argon, CF₄ and O₂, or argon, C₄F₈ and O₂ for oxide etch applications, or other chemistries such as, for example, O₂/CO/Ar/C₄F₈, O₂/Ar/C₄F₈, O₂/CO/AR/C₅F₈, O₂/CO/Ar/C₄F₆, O₂/Ar/C₄F₆, N₂/H₂.

[0047] For example, the number of gas injection orifices 100 formed within electrode plate 24 can range from 1 to 10000. Desirably, the number of gas injection orifices 100 ranges from 50 to 500; and preferably, the number of gas injection orifices 100 is at least 100. Furthermore, for example, a diameter of the gas injection orifice can range from 0.1 to 20 mm. Desirably, the diameter ranges from 0.5 to 5 mm, and preferably the diameter ranges from 0.5 to 2 mm. In addition, for example, a length of a gas injection orifice can range from 1 to 20 mm. Desirably, the length ranges from 2 to 15 mm, and preferably the length ranges from 3 to 12 mm.

[0048] Additionally, as shown in FIG. 3, electrode plate 24 comprises a plenum cavity 84 having a plenum surface 82b that is part of the first surface 82, configured to receive the processing gas, and configured to distribute the processing gas to the plurality of gas injection orifices 100.

[0049] Additionally, electrode plate 24 can comprise a first sealing feature 86a coupled to the coupling surface 82a of the electrode plate 24 and configured to seal the electrode plate 24 with the upper assembly 20. The first sealing feature can, for example, comprise a dovetail cross-section or rectangular cross-section configured for receiving an O-ring. In an alternate embodiment, an electrical coupling feature (not shown) can be integrated with the coupling surface 82a of the electrode plate 24 in order to provide improved electrical coupling between the electrode plate 24 and the upper assembly 20. The electrical coupling feature can, for example, comprise Spirashield (commercially available from Spira Manufacturing Company), known to those skilled in the art of vacuum processing.

[0050] Additionally, electrode plate 24 can comprise a second sealing feature 86b coupled to the coupling surface 82a of the electrode plate 24 and configured to seal the electrode plate 24 with the upper assembly 20. The second sealing feature can, for example, comprise a dovetail cross-section or rectangular cross-section configured for receiving an O-ring. In an alternate embodiment, an electrical coupling feature (not shown) can be integrated with the coupling surface 82a of the electrode plate 24 in order to provide improved electrical coupling between the electrode plate 24 and the upper assembly 20. The electrical coupling feature can, for example, comprise Spirashield (commercially available from Spira Manufacturing Company), known to those skilled in the art of vacuum processing.

[0051] Additionally, electrode plate 24 can comprise one or more third sealing features 86c coupled to the coupling surface 82a of the electrode plate 24 and configured to seal each of the one or more fastening through-holes 112 with the upper assembly 20. The second sealing feature can, for example, comprise a dovetail cross-section or rectangular cross-section configured for receiving an O-ring. In an alternate embodiment, an electrical coupling feature (not shown) can be integrated with the coupling surface 82a of the electrode plate 24 in order to provide improved electrical coupling between the electrode plate 24 and the upper assembly 20. The electrical coupling feature can, for example, comprise Spirashield (commercially available from Spira Manufacturing Company), known to those skilled in the art of vacuum processing.

[0052] The electrode plate 24 can further include a plurality of fastening receptors 110 for receiving fastening devices (not shown), such as a threaded bolt, in order to attach the electrode plate 24 to the upper assembly 20. For example, the number of fastening receptors 110 formed within electrode plate 24 can range from 1 to 100. Desirably, the number of fastening receptors 110 can range from 5 to 20; and, preferably the number of fastening receptors 110 is at least 8.

[0053] As shown in FIG. 2, the electrode plate 24 can further comprise a diagnostics port 120, and a fourth sealing feature 122 coupled to the coupling surface 82a of the electrode plate 24 and configured to seal the diagnostics port 120 with the upper assembly 20. As depicted in FIG. 6, the diagnostics port 120 can include an entrant cavity 124 and an exit through-hole 126 comprising an interior surface 128 contiguous with the plasma surface 90. Similarly, the second sealing feature can, for example, comprise a dovetail cross-section or rectangular cross-section configured for receiving an O-ring. The diagnostics port 120 can be used to couple a diagnostics system (not shown) with the reduced pressure atmosphere 11 of plasma processing chamber 10. For example, the diagnostics system can comprise a pressure manometer.

[0054] Referring again to FIG. 1, FIG. 2, and FIG. 3, deposition shield 26 can, for example, further comprise an opening 130 in order to accommodate access to the process space 12 through deposition shield 26. In an embodiment of the present invention, the opening 130 is formed in deposition shield 26 to accommodate the insertion of at least one of a chamber liner plug (not shown) or an optical window deposition shield such as the one depicted in FIG. 1. For further details, co-pending U.S. patent application Ser. No. 10/259,352, entitled “Method and apparatus for an improved optical window deposition shield in a plasma processing system”, filed on even date herewith, is incorporated herein by reference in its entirety. Alternately, the opening 130 is not formed in deposition shield 26.

[0055] In FIGS. 7A and 7B, an expanded view of opening 130 in deposition shield 26 and a cross sectional view of opening 130, taken along a major axis of opening 130, respectively, are presented. As depicted in FIG. 7B, opening 130 can further comprise a first opening surface 132 coupled to the inner surface 72 of the deposition shield 26, a second mating surface 134 coupled to the outer surface 74 of the deposition shield 26, and a mating surface 136 coupled to the first opening surface 132 and to the second opening surface 134. In addition, the mating surface 136 can comprise at least one tapped hole 138 for receiving a threaded fastener (not shown) in order to couple at least one of the chamber plug (not shown) or the optical window deposition shield (not shown) to the deposition shield 26.

[0056] As shown in FIG. 8, the mating surface 136 further comprises a fastening surface 140 immediately adjacent to and extending within the tapped hole 138. Furthermore, for example, a width (along a major axis) of the opening 130 can range from 1 to 100 mm. Desirably, the width can range from 10 to 40 mm, and preferably, the width is at least 25 mm. Furthermore, for example, a height (along a minor axis) of the opening 130 can range from 1 to 100 mm. Desirably, the height can range from 10 to 40 mm, and preferably, the height is at least 15 mm.

[0057] As illustrated in FIGS. 2 through 8, a plurality of exposed surfaces 145 can comprise the plasma surface 90 (FIG. 3) of the second surface 88 of the electrode plate 24, the inner surface 72 of the cylindrical wall 70 of the deposition shield 26 (FIG. 4), and the distal end lip surface 78 of the distal end surface 76 of the deposition shield 26 (FIG. 4). Additionally, the exposed surfaces 145 can comprise the injection surface 106 (FIG. 5) of the exit region 104 in the plurality of gas injection orifices 100, the interior surface 128 of the exit through-hole 126 in the diagnostics port 120 (FIG. 6), the first opening surface 132 of the opening 130 (FIG. 8), and the mating surface 136 excluding the fastening surface 140 of the opening in the deposition shield (FIG. 8). Alternately, the exposed surfaces comprise all surfaces on the electrode plate 24 with deposition shield 26.

[0058] Referring now to FIGS. 2 through 8, the electrode plate 24 with the deposition shield 26 further comprises a protective barrier 150 formed on the exposed surfaces 145 of the electrode plate 24 with the deposition shield 26. In an embodiment of the present invention, the protective barrier 150 can comprise a compound including an oxide of aluminum such as Al₂O₃. In another embodiment of the present invention, the protective barrier 150 can comprise a mixture of Al₂O₃ and Y₂O₃. In another embodiment of the present invention, the protective barrier 150 can comprise at least one of a III-column element (column III of periodic table) and a Lanthanon element. In another embodiment of the present invention, the III-column element can comprise at least one of Yttrium, Scandium, and Lanthanum. In another embodiment of the present invention, the Lanthanon element can comprise at least one of Cerium, Dysprosium, and Europium. In another embodiment of the present invention, the compound forming protective barrier 150 can comprise at least one of Yttria (Y₂O₃), Sc₂O₃, Sc₂F₃, YF₃, La₂O₃, CeO₂, Eu₂O₃, and DyO₃.

[0059] In an embodiment of the present invention, the protective barrier 150 formed on electrode plate 24 with the deposition shield 26 comprises a minimum thickness, wherein the minimum thickness can be specified as constant across at least one of the exposed surfaces 145. In another embodiment, the minimum thickness can be variable across the exposed surfaces 145. Alternately, the minimum thickness can be constant over a first portion of an exposed surface and variable over a second portion of the exposed surface. For example, a variable thickness can occur on a curved surface, on a corner, or in a hole. For example, the minimum thickness can range from 0.5 micron to 500 micron. Desirably; the minimum thickness can range from 100 micron to 200 micron; and preferably, the minimum thickness is at least 120 micron.

[0060] FIG. 9 presents a method of producing the electrode plate with the deposition shield for the upper electrode in the plasma processing system described in FIG. 1 according to an embodiment of the present invention. A flow diagram 300 begins in 310 with fabricating an electrode plate with the deposition shield (e.g., a plate and shield having the characteristics of the plate and shield described with reference to FIGS. 2–8). Fabricating the electrode plate with the deposition shield can comprise at least one of machining, casting, polishing, forging, and grinding. For example, each of the elements described above can be machined according to specifications set forth on a mechanical drawing, using conventional techniques including a mill, a lathe, etc. The techniques for machining a component using, for example, a mill or a lathe, are well known to those skilled in the art of machining. The electrode plate with the deposition shield can, for example, be fabricated from aluminum.

[0061] In 320, the electrode plate 24 with the deposition shield 26 is anodized to form a surface anodization layer. For example, when fabricating the electrode plate 24 with the deposition shield 26 from aluminum, the surface anodization layer comprises aluminum oxide (Al₂O₃). Methods of anodizing aluminum components are well known to those skilled in the art of surface anodization.

[0062] In 330, the surface anodization layer is removed from the exposed surfaces using standard machining techniques. During the same machining step, or during a separate machining step, other surfaces (e.g., the first surface of the electrode plate excluding the plenum cavity, the first sealing feature, the second sealing feature, the one or more third sealing features, the fourth sealing feature, and the distal end mating surface of the deposition shield) may also be machined (e.g., to produce a flat or bare surface that provides at least one of a good mechanical or electrical contact at the machined surface).

[0063] In 340, a protective barrier 150 (as described above) is formed on the exposed surfaces 145. A protective barrier comprising, for example Yttria, can be formed using (thermal) spray coating techniques that are well known to those skilled in the art of ceramic spray coatings. In an alternate embodiment, forming the protective barrier can further comprise polishing the thermal spray coating. For example, polishing the thermal spray coating can comprise the application of sand paper to the sprayed surfaces.

[0064] FIG. 10 presents a method of fabricating the electrode plate with the deposition shield for the upper electrode in the plasma processing system described in FIG. 1 according to another embodiment of the present invention. A flow diagram 400 begins in 410 with machining an electrode plate 24 with a deposition shield 26. Fabricating the electrode plate with the deposition shield can comprise at least one of machining, casting, polishing, forging, and grinding. For example, each of the elements described above can be machined according to specifications set forth on a mechanical drawing, using conventional techniques including a mill, a lathe, etc. The techniques for machining a component using, for example, a mill or a lathe, are well known to those skilled in the art of machining. The electrode plate with the deposition shield can, for example, be fabricated from aluminum.

[0065] In 420, exposed surfaces 145 are masked to prevent the formation of a surface anodization layer thereon. Techniques for surface masking and unmasking are well known to those skilled in the art of surface coatings and surface anodization. During the same masking step, or during a separate masking step, other surfaces (e.g., the first surface of the electrode plate excluding the plenum cavity, the first sealing feature, the second sealing feature, the one or more third sealing features, the fourth sealing feature, and the distal end mating surface of the deposition shield) may also be masked (e.g., to maintain a flat or bare surface that provides at least one of a good mechanical or electrical contact at the machined surface).

[0066] In 430, the electrode plate with the deposition shield is anodized to form a surface anodization layer on the remaining unmasked surfaces. For example, when fabricating the electrode plate with the deposition shield from aluminum, the surface anodization layer comprise aluminum oxide (Al₂O₃). Methods of anodizing aluminum components are well known to those skilled in the art of surface anodization.

[0067] In 440, the exposed surfaces 145 are unmasked, and a protective barrier 150 is formed on the exposed surfaces 145. A protective barrier comprising, for example Yttria, can be formed using (thermal) spray coating techniques that are well known to those skilled in the art of ceramic spray coatings. In an alternate embodiment, forming the protective barrier can further comprise polishing the thermal spray coating. For example, polishing the thermal spray coating can comprise the application of sand paper to the sprayed surfaces.

[0068] FIG. 11 presents a method of producing the electrode plate with the deposition shield in the plasma processing system described in FIG. 1 according to another embodiment of the present invention. A flow diagram 500 begins in 510 with fabricating an electrode plate 24 with a deposition shield 26. Fabricating the electrode plate with the deposition shield can comprise at least one of machining, casting, polishing, forging, and grinding. For example, each of the elements described above can be machined according to specifications set forth on a mechanical drawing, using conventional techniques including a mill, a lathe, etc. The techniques for machining a component using, for example, a mill or a lathe, are well known to those skilled in the art of machining. The electrode plate can, for example, be fabricated from aluminum.

[0069] In 520, a protective barrier 150 (as described above) is formed on the exposed surfaces 145 of the electrode plate. A protective barrier comprising, for example Yttria, can be formed using (thermal) spray coating techniques that are well known to those skilled in the art of ceramic spray coatings. In an alternate embodiment, forming the protective barrier can further comprise polishing the thermal spray coating. For example, polishing the thermal spray coating can comprise the application of sand paper to the sprayed surfaces.

[0070] In an alternate embodiment of the present invention, a mixture of masking and machining prepares the proper number of surfaces to be protected with a protective barrier 150. For example, the plasma surface of the second surface of the electrode plate may be masked to prevent an anodization layer from being formed thereon, while the injection surface of the exit region in the plurality of gas injection orifices is machined after anodization to present a bare, exposed surface.

[0071] While not necessary in order to form the protective barrier 150 on the exposed surfaces 145, it is also possible to machine other non-exposed surfaces on which an anodization layer has been formed or to mask other non-exposed surfaces prior to performing anodization (e.g., in order to provide a bare surface for an electrical or mechanical connection between parts). Such surfaces may include surfaces of sealing or mating features.

[0072] Although only certain exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.